1. Field of the Invention
The present invention generally relates to an image sensor package, and more particular, to an image sensor package applied in a CMOS camera module (CCM), wherein the unflatness problem caused by the passive components disposed on the lower surface of the substrate in the image sensor package is solved by disposing a bottom cover.
2. Description of Related Art
Computers, handsets, digital cameras and liquid crystal displays are indispensable in the modern people life, but none of them is a product not related to the semiconductor industry. In terms of the peripheral products related to the semiconductor industry, the products are more numerous and various that demonstrates the solid potential and significant importance of the electronic industry. In recent years, along with the rapid increasing demands of customers on the electronic product function, the multifunction, the portability and the light-handiness, the package process manufacturers have switched the process direction from the conventional technology into the high precision process featuring high power, high density, lightness, thinness and miniaturization. In addition to the above-mentioned trend, an electronic package also needs to keep the basic characteristics, such as high reliability, good heat dissipation and low manufacturing cost, so as to confront the challenge of the time urgency for launching a new product and the life time of a product.
Among numerous electronic products, the video multimedia product is the most popular one, while after launching digital cameras, digital camcorders and image scanners, the image digitization has become the necessary trend. The key component and sub-assembly for the above-mentioned video multimedia products is the image sensor. In fact, the image sensor is a semiconductor chip which is able to convert an optical signal into an electronic signal and includes a photo-sensing component, for example, a complementary metal-oxide semiconductor (CMOS). In order to facilitate expanding the CMOS image sensor market, the task that how to make the chip therein have the light-handiness and optimum efficiency is counted as one of the emphases for the future technology developments.
Among the chip packaging technologies, the flip-chip package technology is developed to adapt the light, slim, short and small tendency of a product and usually utilizes the surface array arrangement mode to dispose a plurality of pads on the active surface of a chip, wherein the pads are used to form bumps and the bumps are then used to electrically connect the chip to a substrate. Since the flip-chip package technology is able to be applied in a chip package with high pin count and has other advantages, such as having a less packaging area and shortened signal transmission paths, the flip-chip package technology has been broadly used in the chip packaging field currently.
In addition, to meet the electrical integration design requirement of a chip package, a plurality of passive components, such as capacitors, inductors and resistors, can be further disposed on the surface of a flip-chip packaged substrate. Moreover, the passive components can be electrically connected to the chip or other electronic components through the interconnection traces in the flip-chip packaged substrate. In other words, the chip can be electrically connected to the passive components through bumps and the interconnection traces in the flip-chip packaged substrate.
FIG. 1 is a diagram of a conventional image sensor package. Referring to FIG. 1, the image sensor 1 mainly includes a substrate 10, a plurality of passive components 11, a chip 12 and a lens module 13.
The substrate 10 has an upper surface 101 and a lower surface 102, and the passive components 11 are disposed on the lower surface 102 of the substrate 10 by using a surface mount technology (SMT). After that, a wire bonding procedure is performed on the chip 12 and the substrate 10 so as to electrically connect them to each other, wherein the chip 12 has a photo-sensing component. In the end, the lens module 13 is assembled with and disposed on the substrate 10, and the lens module 13, the substrate 10 and the chip 12 together form a closure space. By this way, when entering into the lens of the lens module 13 and travelling through the lens module 13, the light would irradiate the photo-sensing component, and the action of the light on the photo-sensing component is able to generate an electrical signal.
In consideration of the current trend of the overall dimension of a package to be smaller, while more passive components are disposed therein, the above-mentioned prior art disposing the passive components on the lower surface of the substrate may suffer an inferior flatness on the lower surface of the substrate, which further leads to the signal-testing problem during the final stage of a package process. Thus, the testing yield of the whole package is affected.
In order to solve the problems of the excess number of the passive components and the unflatness on the lower surface of the substrate, an alternative conventional scheme was provided to dispose the passive components on the side edges of the substrate. However, the proposed scheme does not exactly solve the above-mentioned problem since the design scheme to dispose the passive components on the side edges still enlarges the substrate of the package.
In fact, people engaged in fabricating and developing image sensors keep efforts to improve the passive component technique and look forward to solve the unflatness problem in the prior art wherein the passive components are disposed on the lower surface of the CCM substrate with the goal to achieve a good and stable testing yield during testing the CCM image sensor.